This invention relates to devices for interrupting the regular formation of stitches in a sewing machine and more particularly to a solenoid actuated needle bar engaging mechanism in a skip-stitch device.
The usual skip-stitch device in a sewing machine is normally dormant during regular sewing and is generally activated only when a basting operation is required. Thus as it is shown in the U.S. Pat. Nos. 3,559,601 issued Feb. 2, 1971, and 3,782,311 issued Jan. 1, 1974, needle bar endwise reciprocation can be interrupted by causing the needle bar to undergo a lateral excursion beyond the normal range of sewing machine zig-zag motion.
However with the advent of the electronically controlled sewing machines it has been found desirable and necessary to have needle bar endwise reciprocation controlled for reasons other than basting. For example, by interrupting needle bar endwise reciprocation at the instant of selection of a new pattern, placement of a stitch related to the old pattern may be avoided. To accomplish this it is necessary to separate the needle bar from its drive means without the necessity for the extreme excursion required in the prior art devices. This was accomplished as disclosed in U.S. Pat. No. 3,872,809, issued Mar. 25, 1975, by having a solenoid responsive to an electrical signal to pivot a latch release member into engagement with a coupling member to unlatch the coupling member from the needle bar drive member.
The arrangement disclosed in the last noted patent above has been entirely adequate in its application in a sewing machine to effect basting stitches or to disconnect a needle bar concurrent with new pattern selection. It has been noted, however, the continuous actuation of the solenoid during basting results in substantial generation of heat. Also, due to the direct nature of operation of the solenoid, a fairly large device is required.
What is required is a basting stitch mechanism activated by electrical signals so as to be compatible with an electronic control device, which is small in size and with a very low power consumption.